Battery voltage testing systems are generally known and have been used to test and determine the performance of batteries, such as batteries used in vehicles. Further, such systems can be used to analyze the performance of other aspects of a vehicle's electrical system, such as the starting and charging systems.
To properly test the cables and the connections, voltage drops must be measured in the presence of a flowing current and calculations made based thereon using Ohm's Law. Voltage drop measurements under conditions of intermittent current have traditionally been tested by using a variable load tester having an auxiliary voltmeter. The variable load tester has typically been connected at the starter (or alternator) and auxiliary volt leads of the tester connected at the battery.
In such a procedure an operator applies and adjusts the current using the variable load tester. While current flows, the operator notes the voltage at the starter (or alternator), and also notes the voltage at the battery. The operator then subtracts one voltage from the other to obtain the voltage drop of the electrical system. If the voltage drop exceeds a specified amount (typically 0.5 volts), the electrical system is deemed problematic and the operator determines if the problem is in a positive leg or in a negative leg of the electrical system.
This determination is typically made by reconnecting the auxiliary volt leads to measure a voltage drop across the positive leg. The operator then applies and adjusts the load and notes the voltage across the positive leg. The voltage drop cannot exceed one half of a maximal acceptable amount (e.g., 0.25 volts). A value exceeding one half of the maximal acceptable amount indicates a possible defect in the positive leg. To measure the voltage drop across a negative leg of the system, the auxiliary volt leads are moved to the negative leg. A load is applied and adjusted and the voltage drop across the negative leg is measured. A value exceeding one half of the maximal acceptable amount (e.g., 0.25 volts) indicates a possible defect in the negative leg.
Other variations of the aforementioned procedure, in which voltage drops are tested in an electrical system, have been attempted. For example, an inductive current probe can be used to measure the current in the system and a variable load tester can be added to supplement the system load if needed. The operator is thereby allowed to connect the variable load tester at the battery; however, the operator is still required to perform multiple procedures and keep track of and subtract a series of voltages from one another. In addition, such approaches to testing voltage drops in an electrical system require the operator to perform multiple setups to completely test the positive and negative legs of the system.
Because voltage drop tests are so difficult to perform and require a significant amount of knowledge and skill by the operator, they are rarely performed. Often the battery, starter, or alternator is unnecessarily replaced, resulting in operations that fail to solve the underlying problem.
The cranking RPM of a vehicle can oftentimes be used as an indicator of potential problems with various aspects of a vehicle. For example, a low cranking RPM for a vehicle may be indicative of problems with one or more of the battery, electrical system, starting system, starter motor, and/or engine condition. However, measuring the cranking RPM for a vehicle has been difficult. Furthermore, information about the cranking RPM may be used in combination with other information about the vehicle to help diagnose one or more problems or potential problems with different aspects of the vehicle.